forked from Mirrors/opensbi

FW_PIC=y is on by default, but the doc is missing when this was introduced. Add some description for it. Signed-off-by: Bin Meng <bmeng.cn@gmail.com> Reviewed-by: Anup Patel <anup.patel@wdc.com>
FW_PIC=y is on by default, but the doc is missing when this was introduced. Add some description for it. Signed-off-by: Bin Meng <bmeng.cn@gmail.com> Reviewed-by: Anup Patel <anup.patel@wdc.com>